Conventionally, a tap hole is opened in the lower portion of the furnace wall of a blast furnace or the like with a hole opening machine, and, after the tapping, mud is injected into the tap hole with a mud injection machine so as to close the tap hole.
Molten iron and so forth adhere to the tap hole surface and solidify during the tapping, and the tap hole surface often becomes uneven. If such unevenness is present, when closing the tap hole with the mud injection machine, the end face of the injection nozzle of the mud injection machine cannot be in close contact with the tap hole surface, mud leaks to the outside, and the work of injecting mud cannot be performed efficiently. Therefore, conventionally, the tap hole surface is smoothed using an apparatus for smoothing a tap hole surface. FIG. 13 is a diagram showing an example of such a conventional apparatus for smoothing a tap hole surface, reference sign M denotes a mud injection machine, reference sign C denotes an apparatus for smoothing a tap hole surface that is attached to the distal end of the mud injection machine M interchangeably with a mud injection nozzle (not shown), reference sign R denotes a blast furnace, reference sign S denotes a tap hole surface, and reference sign K denotes a smoothed surface.
Heretofore, various apparatuses for smoothing a tap hole surface have been proposed. Conventionally, a typical apparatus for smoothing a tap hole surface is, for example, such that an injection nozzle attached to the distal end of a conventional mud injection machine is removed, and instead a disk-shaped surface smoothing unit having smoothing bits (many hard protrusions) is detachably attached. In the work of smoothing the tap hole surface performed by using such a conventional apparatus for smoothing a tap hole surface, the surface smoothing unit is pressed (slapped) against the tap hole surface with a drive mechanism provided in the conventional mud injection machine (a drive mechanism for moving an injection nozzle attached to the distal end of the mud injection machine toward and away from the tap hole), and the tap hole surface is thereby smoothed.